Uplink Synchronization in Multi-Carrier LTE-Advanced Systems
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Solution Overview
Problem
There is no established method for uplink synchronization between an eNodeB and a User Equipment (UE) in an LTE-Advanced multi-carrier system, which is essential for maintaining communication efficiency and peak data rates.
Innovation Solution
The eNodeB selects component carriers without uplink synchronization and transmits a Timing Advance (TA) to the UE, allowing the UE to perform uplink transmission, and subsequently, the eNodeB and UE maintain synchronization timers to adjust and verify the TA, ensuring synchronization across multiple carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is introduced to improve peak rates and spectrum utilization, then system capacity and data rates are improved, but uplink synchronization control becomes complex and is not supported by existing LTE mechanisms
Solution Approach 1:
The patent segments the uplink synchronization control into two distinct approaches: (1) independent random access procedure for each component carrier, and (2) timing advance command-based adjustment using a reference component carrier. This segmentation allows the system to handle multiple carriers without requiring complete redesign of the synchronization mechanism, thereby managing complexity while supporting carrier aggregation for improved peak rates.
Solution Approach 2:
The patent applies preliminary action by establishing uplink synchronization on a reference component carrier first, then using the obtained timing advance value as a basis for other component carriers. This preliminary synchronization establishment simplifies subsequent synchronization control across multiple carriers, avoiding the need for completely independent synchronization procedures for each carrier.
2Measurement precision
If independent random access is performed for each component carrier to establish uplink synchronization, then synchronization accuracy is improved, but signaling overhead and access delay increase
Solution Approach 1:
The patent applies partial action by performing independent random access procedures only when necessary (e.g., when timing advance values differ significantly between carriers or when synchronization accuracy requirements demand it). For other cases, the system uses the more efficient timing advance command-based adjustment method, thereby reducing overall access delay while maintaining sufficient synchronization accuracy.
3Productivity
If timing advance commands are used to adjust uplink transmission timing, then synchronization maintenance efficiency is improved, but timing advance value accuracy may deteriorate without proper validation
Solution Approach 1:
The patent implements feedback mechanisms where the user equipment validates received timing advance commands by checking consistency with previously stored timing advance values and current uplink transmission timing requirements. This feedback validation ensures timing advance value accuracy is maintained while allowing efficient command-based synchronization adjustment, preventing erroneous timing adjustments that would deteriorate synchronization.
Data Source
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Figure 3
Figure 4A~4C
AI summary
A method for uplink synchronization in a multi-carrier system includes the following steps: a base station selects one or more first component carriers, which do not establish the uplink synchronization with the base station, from multiple component carriers supported by a terminal; then the base station obtains Timing Advance (TA) needed by the terminal to perform the uplink transmission on the first component carriers, and sends the TA information to the terminal; the terminal performs the uplink transmission on said first component carriers according to said TA. The application of the present invention enables the establishment of uplink synchronization between the base station and the user equipment in multi-carrier system.